This invention relates to valves and, more particularly, to an improved diaphragm valve for regulating gas flow, wherein movement of the flexible diaphragm between zero flow configuration and a full flow configuration is effected without stretching the diaphragm.
Current devices for regulating fluid flow include throttling devices with orifices and valves actuated by lever mechanisms and pan-type rubber diaphragms to vary the orifice opening. These devices rely on the principle of equilibrium of forces to control pressure and suffer from elevated pressure effects, i.e., the outlet pressure varies as a function of the inlet pressure. Also, fluid flow capacities are restricted by the size of the orifice, which in turn is limited to the available shut off force.
Other devices employ slotted cages and molded rubber sleeves (or boots) that peel from the cage slots to throttle fluid flow. Sleeve and boot-type valves each have limitations. These valves have poor stability at low fluid flow rates through the valve. The fluid stream usually impinges substantially on the sleeve and deflects the fluid stream, thereby subjecting the sleeve to erosion. Other difficulties encountered are stretching and extrusion of the rubber sleeves as well as difficulties in the assembly, operation and use of such prior valves.
It is therefore apparent that a need exists for a fluid flow regulating valve which does not suffer from the above-enumerated deficiencies. A need also exists for such a valve which is easily serviced, without requiring removal of the entire valve from the pipeline in which it is installed.